Electric machine with locally-tuned properties

ABSTRACT

A rotor includes a rotor core lamination. The rotor core lamination includes a first metal alloy that at least partially defines adjacent magnet pockets proximate an outer periphery of the rotor core lamination. The rotor core lamination further includes a second metal alloy different than the first metal alloy that forms at least a portion of a bridge that extends between the magnet pockets. The rotor core lamination further includes permanent magnets disposed in the magnet pockets at opposing sides of the second metal alloy.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 16/123,321filed Sep. 6, 2018, the disclosure of which is hereby incorporated inits entirety by reference herein.

TECHNICAL FIELD

The present disclosure relates to an electric machine assembly of anelectrified vehicle.

BACKGROUND

Extended drive range technology for electrified vehicles, such asbattery electric vehicles (BEVs), hybrid electric vehicles (HEVs), andplug in hybrid vehicles (PHEVs), is continuously improving. Achievingthese increased ranges, however, often requires traction batteries andelectric machines to have higher power outputs and associated thermalmanagement systems with increased capacities in comparison to previousBEVs and PHEVs. Improving efficiency between electric machine statorcores and rotors may increase power outputs of the electric machines.

SUMMARY

In at least one approach, a method of forming a rotor lamination isprovided. The method may include, with a laser, fabricating a firstregion of a rotor lamination layer with a first powdered metal having afirst composition. The method may further include, with a laser,fabricating a second region of the rotor lamination layer in contactwith the first region with a second powdered metal having a secondcomposition different than the first composition. The first and secondregions may be fabricated in a common lamination plane.

In at least one approach, a rotor is provided. The rotor may include arotor core lamination. The rotor core lamination may include a firstmetal alloy that at least partially defines adjacent magnet pocketsproximate an outer periphery of the rotor core lamination. The rotorcore lamination may further include a second metal alloy different thanthe first metal alloy that forms at least a portion of a bridge thatextends between the magnet pockets. The rotor may further includepermanent magnets disposed in the magnet pockets at opposing sides ofthe second metal alloy.

In at least one approach, an electric machine is provided. The electricmachine may include a stack of interlocked rotor core laminations.Individual rotor core laminations of the interlocked rotor corelaminations may include a mortise extending therein and anintegrally-formed tenon extending therefrom. The tenons may interfacewith the mortises to interlock adjacent rotor core laminations. A firstindividual rotor core lamination may have a first mortise having a depthextending into the first individual rotor core lamination. A secondindividual rotor core lamination may have a first integrally-formedtenon having a height extending therefrom. The height of the firstintegrally-formed tenon may correspond to the depth of the firstmortise.

In at least one approach, a method of forming a rotor lamination isprovided. The method may include, with a laser, fabricating a firstregion of a lamination layer with a first powdered metal having a firstcomposition. The first region may at least partially define a magnetpocket. The method may further include, with a laser, fabricating asecond region of the lamination layer with a second powdered metalhaving a second composition different than the first composition. Thesecond region may be disposed immediately adjacent the first region.

In at least one approach, a rotor is provided. The rotor includes alamination containing a pair of permanent magnets that may be disposedin adjacent magnet pockets at an outer periphery of the lamination. Thelamination may include a first metal alloy that at least partiallydefines a cavity disposed between at least portions of the magnetpockets. The lamination may include a second metal alloy different thanthe first metal alloy and that may form at least a portion of a bridgethat extends between the magnet pockets.

In at least one approach, a rotor core is provided. The rotor core mayinclude a stack of interlocked laminations. The interlocked laminationsmay include a first lamination, a second lamination, and a thirdlamination. The first lamination may have a first wedge extendingtherefrom. The second lamination may be secured to the first laminationand may have a first notch extending therein and a second wedgeextending therefrom. The first wedge may be received within the firstnotch. The third lamination may be secured to the second lamination andmay have a second notch extending therein. The second wedge may bereceived within the second notch.

In at least one approach, a method of forming a rotor core is provided.The method may include fabricating a first lamination having a firstwedge, a second lamination having a first notch and a second wedge, anda third lamination having a second notch. The method may further includeaffixing the first lamination to the second lamination such that thefirst wedge is disposed within the first notch. The method may furtherinclude affixing the second lamination to the third lamination such thatthe second wedge is disposed within the second notch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an example of an electrifiedvehicle.

FIG. 2 is a perspective, exploded view of an example of a portion of anelectric machine.

FIG. 3 is a top view of a rotor.

FIG. 4 is a side view of the rotor of FIG. 3 showing stacked rotorlaminations.

FIG. 5 is a rotor portion having a first arrangement of first and secondregions.

FIG. 6 is powder bed for a rotor portion that has the first arrangementof first and second regions.

FIG. 7 is a rotor portion having a second arrangement of first andsecond regions.

FIG. 8 is a rotor portion and a stator portion having a thirdarrangement of first and second regions.

FIG. 9 is a rotor portion and a stator portion having a fourtharrangement of first and second regions.

FIG. 10 is a rotor portion having an arrangement of air pockets.

FIG. 11 is stack of rotor laminations having an arrangement ofcooperating wedges and notches.

FIG. 12 depicts a first punch and die for creating an opening in alamination when the punch is deployed.

FIG. 13 depicts an additive manufacturing operation for a firstlamination.

FIG. 14 depicts a first electric machine lamination formed throughpunching and additive manufacturing processes.

FIG. 15 depicts a second punch and die for creating an opening in alamination when the punch is deployed.

FIG. 16 depicts an additive manufacturing operation for a secondlamination.

FIG. 17 depicts a second electric machine lamination formed throughpunching and additive manufacturing processes.

FIG. 18 depicts a first stack of electric machine laminations.

FIG. 19 depicts a second stack of electric machine laminations.

FIG. 20 depicts a sequence of operations for blasting a rotor of anelectric machine.

FIG. 21 depicts a sequence of operations for masking and blasting arotor of an electric machine.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments may take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures may be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

FIG. 1 is a schematic diagram illustrating an example of an electrifiedvehicle. In this example, the electrified vehicle is a PHEV referred toas a vehicle 12 herein. The vehicle 12 may include one or more electricmachines 14 mechanically connected to a hybrid transmission 16. Theelectric machines 14 may be capable of operating as a motor or agenerator. In addition, the hybrid transmission 16 may be mechanicallyconnected to an engine 18. The hybrid transmission 16 may also bemechanically connected to a drive shaft 20 that may be mechanicallyconnected to wheels 22. The electric machines 14 can provide propulsionand deceleration capability when the engine 18 is turned on or off. Theelectric machines 14 may also operate as generators and provide fueleconomy benefits by recovering energy that would normally be lost asheat in the friction braking system. The electric machines 14 may alsoprovide reduced pollutant emissions since the vehicle 12 may be operatedin electric mode under certain conditions.

A traction battery 24 may store energy that can be used by the electricmachines 14. The traction battery 24 may typically provide a highvoltage DC output from one or more battery cell arrays, sometimesreferred to as battery cell stacks, within the traction battery 24. Thebattery cell arrays may include one or more battery cells. The tractionbattery 24 may be electrically connected to one or more powerelectronics modules 26 through one or more contactors (not shown). Theone or more contactors may isolate the traction battery 24 from othercomponents when opened and connects the traction battery 24 to othercomponents when closed. The power electronics module 26 may also beelectrically connected to the electric machines 14 and may provide theability to bi-directionally transfer electrical energy between thetraction battery 24 and the electric machines 14. For example, a typicaltraction battery 24 may provide a DC voltage while the electric machines14 may require a three-phase AC voltage to function. The powerelectronics module 26 may convert the DC voltage to a three-phase ACvoltage as required by the electric machines 14. In a regenerative mode,the power electronics module 26 may convert the three-phase AC voltagefrom the electric machines 14 acting as generators to the DC voltagerequired by the traction battery 24. Portions of the description hereinare equally applicable to a pure electric vehicle. For a pure electricvehicle, the hybrid transmission 16 may be a gear box connected to anelectric machine 14 and the engine 18 may not be present.

In addition to providing energy for propulsion, the traction battery 24may provide energy for other vehicle electrical systems. A typicalsystem may include a DC/DC converter module 28 that converts the highvoltage DC output of the traction battery 24 to a low voltage DC supplythat is compatible with other vehicle loads. Other high-voltage loads,such as compressors and electric heaters, may be connected directly tothe high-voltage without the use of a DC/DC converter module 28. In atypical vehicle, the low-voltage systems are electrically connected toan auxiliary battery 30 (e.g., a twelve-volt battery).

A battery electrical control module (BECM) 33 may be in communicationwith the traction battery 24. The BECM 33 may act as a controller forthe traction battery 24 and may also include an electronic monitoringsystem that manages temperature and charge state of each battery cell ofthe traction battery 24. The traction battery 24 may have a temperaturesensor 31 such as a thermistor or other temperature gauge. Thetemperature sensor 31 may be in communication with the BECM 33 toprovide temperature data regarding the traction battery 24.

The vehicle 12 may be recharged by an external power source 36 such asan electrical outlet. The external power source 36 may be electricallyconnected to an electric vehicle supply equipment (EVSE) 38. The EVSE 38may provide circuitry and controls to regulate and manage the transferof electrical energy between the power source 36 and the vehicle 12. Theexternal power source 36 may provide DC or AC electric power to the EVSE38. The EVSE 38 may have a charge connector 40 for plugging into acharge port 34 of the vehicle 12. The charge port 34 may be any type ofport configured to transfer power from the EVSE 38 to the vehicle 12.The charge port 34 may be electrically connected to a charger oron-board power conversion module 32. The power conversion module 32 maycondition the power supplied from the EVSE 38 to provide the propervoltage and current levels to the traction battery 24. The powerconversion module 32 may interface with the EVSE 38 to coordinate thedelivery of power to the vehicle 12. The charge connector 40 may havepins that mate with corresponding recesses of the charge port 34.

The various components discussed above may have one or more associatedcontrollers to control and monitor the operation of the components. Thecontrollers may communicate via a serial bus (e.g., a controller areanetwork (CAN)) or via discrete conductors.

The battery cells of the traction battery 24, such as a prismatic orpouch-type cell, may include electrochemical elements that convertstored chemical energy to electrical energy. Prismatic cells orpouch-type cells may include a housing, a positive electrode (cathode)and a negative electrode (anode). An electrolyte may allow ions to movebetween the anode and cathode during a discharge operation, and thenreturn during a recharge operation. Terminals may allow current to flowout of the battery cells for use by the vehicle. When positioned in anarray with multiple battery cells, the terminals of each battery cellmay be aligned with opposing terminals (positive and negative) adjacentto one another and a busbar may assist in facilitating a seriesconnection between the multiple battery cells. The battery cells mayalso be arranged in parallel such that similar terminals (positive andpositive or negative and negative) are adjacent to one another.

FIG. 2 is a partially exploded view illustrating an example of portionsof an electric machine for an electrified vehicle, referred to generallyas an electric machine 100. The electric machine may include a statorcore 102 and a rotor 106. As mentioned above, electrified vehicles mayinclude two electric machines. One of the electric machines may functionprimarily as a motor and the other may function primarily as agenerator. The motor may operate to convert electricity to mechanicalpower and the generator may operate to convert mechanical power toelectricity. The stator core 102 may define an inner surface 108 and acavity 110. The rotor 106 may be sized for disposal and operation withinthe cavity 110. The rotor 10 may include a stack of laminations, asdiscussed in greater detail elsewhere herein. A shaft 112 may beoperably connected to the rotor 106 and be coupled to other vehiclecomponents to transfer mechanical power therefrom.

Windings 120 may be disposed within the cavity 110 of the stator core102. In an electric machine motor example, current may be fed to thewindings 120 to obtain a rotational force on the rotor 106. In anelectric machine generator example, current generated in the windings120 by a rotation of the rotor 106 may be used to power vehiclecomponents. Portions of the windings 120, such as end windings 126, mayprotrude from the cavity 110. During operation of the electric machine100, heat may be generated along the windings 120 and end windings 126.The rotor 106 may include magnets such that rotation of the rotor 106 incooperation with an electric current running through the end windings126 generates one or more magnetic fields. For example, electric currentrunning through the end windings 126 may generate a rotating magneticfield. Magnets of the rotor 106 may magnetize and rotate with rotatingmagnetic field to rotate the shaft 112 for mechanical power.

Referring to FIGS. 3 and 4, a rotor 200 may be formed of a plurality oflaminations or lamination layers 202. The rotor 200 may include aplurality of pairs of permanent magnets 204 generating magnetic polesspaced around a perimeter of the rotor. A center opening or hole 206 isprovided on an inner diameter, surface, or edge of the rotor to engagean output shaft. The hole 206 extends about an axis of rotation 208.

A number of bridges connect the material surrounding permanent magnetpockets 210. A center bridge 212 extends radially between the pockets210. Top side bridges 214 extend circumferentially outside of thepockets 210. The combination of each center bridge with the pair ofouter top side bridges holds the part of the lamination beyond thebridges and the magnets 204 under centrifugal load. Mechanically, thebridges allow the rotor to reliably withstand centrifugal loads causedby the rotor being electromagnetically driven during operation of theelectric machine. However, the bridges also lead to magnetic fluxleakage, which reduces the output torque and efficiency of the electricmachine. Thus, thin bridges are electromagnetically desirable to enablehigh torque output and motor efficiency. The balance between strengthand performance leads to a fundamental trade-off between mechanical andelectromagnetic design.

Additionally, the V-shaped orientation of the pockets 210 holdingpermanent magnet pairs 204 define a solid mass nested in the center ofthe V portion. Peripheral cavities 220, or holes, are provided in acenter portion of the solid mass. The peripheral cavities 220 areadjacent to an outer surface of the rotor 200 and create thin materialportions at the outer top side bridge 214 between the permanent magnets204. Larger cavities 220 may reduce more of the mass of the rotorlamination which needs to be held by the bridges.

The lamination 200 may define, or may include, perimeter bridges 230,234. For example, one or more perimeter bridges 230 may be provided thatmay extend between pockets 210 and the outer perimeter 232 of thelamination 200. One or more perimeter bridges 234 may extend betweenperipheral cavities 220 and the outer perimeter 232 of the lamination200.

A lamination may be uniform (or substantially uniform) in composition.For example, a uniform Iron-Silicon (FeSi) alloy may be processedthrough hot rolling, annealing, and cold rolling into a thin electricalsteel sheet with homogeneous chemical composition and physicalproperties. Rotor and/or stator lamination cores may be formed from theelectrical steel sheet by die punching and subsequently stacking thepunched laminations together. Punching rotor and/or stator laminationsfrom an electrical steel sheet that has homogeneous properties mayresult in identical property characteristics within the rotor or statorlamination. However, an electric machine may have conflicting propertyrequirements for different regions within a lamination. For example, inthe bridge areas of a rotor (e.g., center bridge 212 and/or perimeterbridges 230 of FIG. 3), it may be desirable to reduce the magneticpermeability of a lamination in order to reduce flux leakage andincrease torque density. In contrast, for the other regions within therotor lamination, high permeability is desired to assure a largemagnetic induction for high torque density. Therefore, it may bedesirable to suppress the permeability only in selected regions of therotor lamination.

In at least one approach, the lamination 200 may be provided withvarious compositions. The various compositions may be achieved, forexample, by forming the lamination 200 through a fabrication processsuch as an additive manufacturing process (which may also be referred toas three-dimensional printing). In an additive manufacturing process, anobject is built up, layer by layer, via selective deposition ofmaterial. Two examples of additive manufacturing using metals includeDirect Metal Laser Sintering (DMLS) and Laser Deposition (LD). Eachprocess utilizes the consolidation of powder with a laser heatingsource. As such, a laser head 240 may be provided to direct a laser.

To make a lamination core with the DMLS process, a computer-controlledlaser is rastered across a pre-laid bed of metal powder, consolidatingonly the powder that was subjected to the laser heating. After a layerhas been consolidated, a thin electrical insulation layer may be appliedto the surface of the layer. An inorganic ceramic coating (e.g., havinga high-temperature rating) may be chosen as the insulation layer. Inthis way, the insulation layer may endure high-temperature laser heatingduring subsequent metal layer depositions. A new layer of powder maythen be brushed over the work piece and the consolidation step may berepeated. Once the lamination core is completed, it may be removed fromthe loose powder and may subsequently be heat-treated or finish-machinedto remove the rough outer surface layer.

To make a lamination core with the LD process, metal powder may beintroduced directly into a laser beam as a build head rasters over thework piece. The laser may create a liquid melt pool as it rasters, whichmay allow for a dense component to be built up, layer-by-layer, atselected positions. In between the adjacent layer depositions, theinorganic high-temperature-resistant ceramic coating may be applied toprovide electrical insulation between the layers.

Forming a lamination core through additive manufacturing may allow forthe use of custom compositions, for example, by introducing differentelemental or alloy powders during the fabrication process at differentspatial locations. This allows for strategically modifying physicalproperties of lamination cores within the 2D lamination plane. In thisway, and as described in the various examples to follow, a rotorlamination may have locally-tuned properties. The locally-tunedproperties may include, for example, magnetic permeability, mechanicalstrength, loss and magnetic flux density.

In at least one approach, a method of forming a rotor laminationincludes fabricating, with a laser, a first region of a lamination layerwith a first powdered metal. The first powdered metal may have a firstcomposition. The first composition may be, for example, an iron-silicon(FeSi) alloy. The FeSi alloy may have approximately 0.1% toapproximately 4.5% silicon by weight. The first region may at leastpartially define a magnet pocket. The method may further include, with alaser, fabricating a second region of the lamination layer with a secondpowdered metal. The second powdered metal may have a second compositionthat is different than the first composition. In at least one approach,the second powdered metal may have a lower magnetic permeability thanthe first powdered metal. For example, the second powdered metal may bea non-ferromagnetic austenite stainless steel.

As such, the second region discussed herein may have a higher fluxdensity than the first region. The second region may have lower coreloss than the first region. The second region may have higher mechanicalstrength than the first region.

The first and second regions may be formed in a common lamination plane.The second region may be disposed adjacent (e.g., immediately adjacent)to the first region. In this way, the second region may abut the firstregion.

In at least one approach, permeability of local regions may be adjustedby changing the atmosphere during layer deposition. As such, the methodmay further include, prior to fabricating the first region, providing aninert gas atmosphere proximate the laser. The inert gas atmosphere maybe, or may include, argon. The method may further include, prior tofabricating the second region, providing reactive gas atmosphereproximate the laser. The reactive gas atmosphere may be, or may include,oxygen.

Referring to FIG. 5, a portion of a rotor lamination 250 is shown. Therotor lamination 250 may include a first region 252 and one or moresecond regions 254. As discussed, the first region 252 may be formed ofa first material, and the second region 254 may be formed of a secondmaterial different than the first material. The first region 252 may beformed of an FeSi alloy. In this way, the first region 252 may have ahigh permeability.

The first region 252 may define pockets 260 (e.g., two adjacent pockets260) for retaining permanent magnets 262, which generate a magnetic poleof the rotor. The pockets 260 may have a V-shape to form legs. Thepockets 260 may have any shape. For example, the pockets may beV-shaped, U-shaped, or linearly shaped. The legs may extend from avertex of the V-shape, a respective common point on the U-shape (e.g.,the bite), or comprise halves of the linear shape. The legs may bedefined by an edge of the magnet 262, pockets 260, or a center line ofthe magnet 262.

To suppress magnetic permeability in certain spatial locations, therotor lamination 250 may be provided with a custom compositionarrangement. In this way, one or more second regions 254 may beprovided. The material of the second region 254 may be, for example,non-ferromagnetic austenite stainless steel, which may have a highchromium content. In at least one approach, 304L stainless steel (suchas Fe68Cr20Ni10Mn1Si0.3 in wt. %) or 316L may be provided in the secondregion 254.

The second region 254 may include a central bridge 270 that may extendbetween the pockets 260. In at least one approach, a first side 270 a ofthe central bridge 270 forms a wall of a magnet pocket 260, and a secondside 270 b of the central bridge 270 opposite the first side 270 a mayform a wall of an adjacent magnet pocket 260.

The second region 254 may also include a peripheral bridge 272. Theperipheral bridge 272 may extend between a magnet pocket 260 and anouter periphery 274 of the rotor lamination. In at least one approach, afirst side 272 a of the peripheral bridge 270 may form a wall of amagnet pocket 260, and a second side 272 b of the peripheral bridge 270opposite the first side 272 a may form an outermost circumferential wall276 of the rotor lamination 250.

As a LD process usually contains several nozzles, different elemental oralloy powders can be drawn from hoppers to the nozzles and introducedinto the laser. Compositions can be changed strategically when the buildhead rasters at different locations of the deposition layer. Forexample, when moving to the bridge areas of the rotor lamination, thepowder can be changed from FeSi to FeCrNiMnSi (e.g., 304L stainlesssteel).

In addition to elemental chromium, manganese, and nickel, other elementssuch as aluminum, silicon, carbon, sulfur, and/or germanium can also beintroduced into the regions in which lower permeability is desired.

In the approach shown in FIG. 5, the additive manufacturing process mayallow for net-shape part creation.

Referring to FIG. 6, during a DMLS process, the chemical composition ofa laid metal powder bed 280 may vary according to the relative positionon the lamination plane. The laid powder bed 280 may include a firstregion 252′ and one or more second regions 254′. To facilitate theconsolidation of the powder, operating parameters (e.g., the power ofthe laser, laser travel speed, laser spot size, and working height etc.)may also be varied when consolidating different regions with differentpowder compositions (the first and second regions 252, 254).

Referring to FIG. 7, a portion of a rotor lamination 300 is shown. Therotor lamination 300 may include a first region 302 and one or moresecond regions 304. As discussed, the first region 302 may be formed ofa first material, and the second region 304 may be formed of a secondmaterial different than the first material. The first region 302 may beformed of an FeSi alloy. In this way, the first region 302 may have anormal mechanical strength. The second region 304 may have a compositionthat includes higher concentrations (relative to the first region 302)of one or more of aluminum, silicon, sulfur, and germanium. Suchelements may create structure defects in the rotor lamination 300, whichmay impede dislocation motion and therefore may improve mechanicalstrength.

In at least one approach, the center and perimeter bridge areas of therotor lamination 300 are both nonmagnetic and have high mechanicalstrength. As such, non-ferromagnetic and ultrahigh strength metal alloyssuch as Ti alloys and high strength steel can be deployed in the secondregions 304.

Mechanical strength in the second regions 304 may also be improvedthrough grain boundary strengthening. For polycrystalline metals such asFeSi laminations, grain size may influence the mechanical properties.For example, mechanical strength may increase with decreasing grainsize. In this way, the metal deposition parameters such as the rate ofpowder feed, laser power, laser travel speed, laser tilt angle, workingheight, laser spot size may be adjusted locally to reduce laminationgrain size and improve its mechanical strength. Such parameters may beadjusted while keeping the chemical composition unchanged within thelamination plane.

Referring to FIG. 8, a portion of a rotor lamination 310 and a portionof a stator lamination 312 are shown. The rotor and stator laminations310, 312 may include a first region 314 and one or more second regions316. As discussed, the first region 314 may be formed of a firstmaterial, and the second region 316 may be formed of a second materialdifferent than the first material. The first region 314 may be formed ofan FeSi alloy. In this way, the first region 314 may have a normal coreloss.

The second regions 316 may be disposed in regions that experienceincreased core loss; for example, at the outer rim of the rotor and atthe teeth edges of the stator. In this way, the second region may extendabout an entire outer circumference of the rotor lamination layer 310.In the second regions 316, the composition of the powder used duringmanufacturing processes (such as DMLS or LD processes) can be varied byadding higher concentrations of elemental aluminum, silicon, or alloysthereof with iron. For example, whereas the first region 314 may be anFeSi composition with approximately (e.g., +/−0.5%) 3% silicon byweight, the second regions 316 may be an FeSi composition withapproximately (e.g., +/−0.5%) 6.5% silicon by weight. As such, thesecond regions 316 may have higher resistance and may lead to local lossreduction.

Referring to FIG. 9, a portion of a rotor lamination 320 and a portionof a stator lamination 322 are shown. The rotor and stator laminations320, 322 may include a first region 324 and one or more second regions326. As discussed, the first region 324 may be formed of a firstmaterial, and the second region 326 may be formed of a second materialdifferent than the first material. The first region 324 may be formed ofan FeSi alloy. In this way, the first region 324 may have a normalmagnetization. The second area 326 may be provided with a higherpercentage of cobalt or cobalt alloys as compared to the first region324. In this way, the second region 326 may have a higher magnetizationthan the FeSi electrical steel of the first region 324.

The second regions 326 may be disposed in regions that requiresincreased magnetic flux density; for example, at portions of the outerrim of the rotor and at the teeth of the stator. In at least oneapproach, a second region 326 of the rotor lamination 320 extends alongan outer circumference of the lamination layer from a perimeter of amagnet pocket 328 to a perimeter of a cavity 330 located proximate theouter circumference of the lamination layer.

Referring to FIG. 10, a portion of a rotor lamination 340 is shown. Therotor lamination 340 may include a first metal alloy 342 defining afirst region, and may include a second metal alloy defining one or moresecond regions disposed in any location or combination locationspreviously discussed. For example, the second metal alloy may form atleast a portion of a bridge that extends between the magnet pockets, asshown and discussed with respect to FIGS. 5-7. The first metal alloy 342may define one or more air pockets 344. For example, the first metalalloy 342 may define an air pocket 344 that may be disposed radiallybetween at least portions of two adjacent magnet pockets 346 and aradially-inboard surface 348 of the lamination layer 340.

As such, in at least one approach, a method of forming a rotorlamination is provided. The method may include, with a laser,fabricating a first region of a rotor lamination layer with a firstpowdered metal having a first composition. The method may furtherinclude, with a laser, fabricating a second region of the rotorlamination layer in contact with the first region with a second powderedmetal having a second composition different than the first composition.The first and second regions may be fabricated in a common laminationplane. The method may further include forming a plurality of magnetpockets proximate an outer periphery of the rotor lamination layer. Thefirst region may at least partially define the magnet pockets. Thesecond region may include a central bridge that extends between themagnet pockets. The central bridge may form a wall of at least one ofthe magnet pockets.

The second region may also, or may instead, include a peripheral bridge.The peripheral bridge may extend between at least one of the magnetpockets and an outer periphery of the rotor lamination. A first side ofthe peripheral bridge may form a wall of at least one of the magnetpockets. A second side of the peripheral bridge opposite the first sidemay form an outermost circumferential wall of the rotor lamination.

In at least one approach, the first powdered metal may have a highermagnetic permeability than the second powdered metal. The first powderedmetal may have a higher core loss than the second powdered metal. Thesecond powdered metal may have a higher flux density than the firstpowdered metal. In one example approach, the first powdered metal may bean iron-silicon alloy having approximately 0.1% to approximately 4.5%silicon by weight. The second powdered metal may be a non-ferromagneticmaterial.

The method may further include forming, while fabricating the firstregion, a pocket devoid of powdered metal. The pocket may be disposedradially between at least a portion of a magnet pocket and aradially-inboard surface of the lamination layer.

In at least one approach, the method may further include, prior tofabricating the first region, providing an inert gas atmosphereproximate the laser beam and a powder bed. The method may furtherinclude, prior to fabricating the second region, providing a reactivegas atmosphere proximate the laser beam and the powder bed.

As such, a rotor may be provided with a rotor core lamination. The rotorcore lamination may include a first metal alloy that at least partiallydefines adjacent magnet pockets proximate an outer periphery of therotor core lamination. The rotor core lamination may further include asecond metal alloy different than the first metal alloy that forms atleast a portion of a bridge that extends between the magnet pockets. Thefirst metal alloy may have a higher magnetic permeability than thesecond metal alloy. The second metal alloy may have a smaller grain sizethan the first metal alloy. The second metal alloy may define peripheralbridges that extend between the magnet pockets and the outer peripheryof the rotor core lamination. The second metal alloy may extend about anentire outer circumference of the rotor core lamination. The first metalalloy may define an air pocket disposed radially between an inboardregion of the rotor core lamination and the magnet pockets. The rotorcore lamination may further include permanent magnets disposed in themagnet pockets at opposing sides of the second metal alloy.

Referring now to FIG. 11, a method of forming a rotor core may includefabricating a plurality of laminations 350, which may include a firstlamination 350 a, a second lamination 350 b, a third lamination 350 c,and a fourth lamination 350 d. The laminations 350 may include acombination of mortises 352 and tenons 354. For example, the firstlamination 350 a may have a first tenon 354 a, the second lamination 350b may have a first mortise 352 b and a second tenon 354 b, and the thirdlamination 350 c may have a second mortise 352 c. The method may includeaffixing the first lamination 350 a to the second lamination 350 b suchthat the first tenon 354 a is disposed within the first mortise 352 b.The method may further include affixing the second lamination 350 b tothe third lamination 350 c such that the second tenon 354 b is disposedwithin the second mortise 352 c.

As used herein, a mortise may be referred to as a notch, recess,indentation, etc. As used herein a tenon may be referred to as a wedge,protrusion, etc. The tenons may be integrally formed with thelaminations (e.g., formed from the same material). As such, thelaminations, at the areas of the mortises and tenons, may beintegrally-formed, one-piece, unitary laminations.

In at least one approach, the first tenon 354 a may have a height thatcorresponds to (e.g., is the same as or is just less than) a depth ofthe first mortise 352 b. Similarly, the second tenon 354 b may have aheight that corresponds to (e.g., is the same as or is just less than) adepth of the second mortise 352 c.

In this way, the tenons 354 may be used as interlocks to fix adjacentlaminations into a solid core 360. Such three-dimensional laminationlayers may have increased stiffness as compared with flat sheets.Furthermore, such three-dimensional lamination layers may provideimproved core NVH performance.

As such, an electric machine may be provided. The electric machine mayinclude a stack of interlocked rotor core laminations. Individual rotorcore laminations of the interlocked rotor core laminations may include amortise extending therein and an integrally-formed tenon extendingtherefrom. The tenons may interface with the mortises to interlockadjacent rotor core laminations.

In at least one approach, a first individual rotor core lamination mayhave a first mortise having a depth extending into the first individualrotor core lamination. A second individual rotor core lamination mayhave a first integrally-formed tenon having a height extendingtherefrom. The height of the first integrally-formed tenon maycorrespond to the depth of the first mortise.

The additive manufacturing of rotor and/or stator laminationscontemplated herein is flexible. For example, instead of making anentire core layer-by-layer using an additive manufacturing method, onlya single layer, or multiple layers but not all layers, may be formedthrough additive manufacturing. Furthermore, the local physicalproperties of the single rotor or stator lamination can be fine-tunedduring the additive manufacturing process, as discussed herein.Lamination layers may be coated with an insulation layer and may bestacked together to build rotor and stator cores.

Furthermore, it is expressly contemplated that the arrangement of thesecond regions described with respect to FIGS. 5-9 may be combined,rearranged, or otherwise altered.

During the core building process, the bonding between different layersof additive manufacturing-formed laminations can be achieved by applyinga thin layer of adhesive after the insulation layer is applied. Theadhesive bonding may then be cured at either room temperature or hightemperature.

The above described methods are directed toward reducing core loss in anelectric machine. For some applications, the electrical device core maybe processed to reduce magnetic permeability of the device. Plasticdeformation changes the magnetic properties of the electrical device.For example, magnetic permeability decreases in the presence of plasticdeformation of the lamination. In particular, plastic deformation may beintroduced by deforming the laminations in predetermined locations todecrease magnetic permeability in selected areas of the laminations.

As above, the laminations may be formed from sheets of electrical steel.The electrical steel sheets may be of a predetermined thickness. Theelectrical steel sheets may be punched to create rotor laminations andstator laminations. The laminations may be derived from one or more ofthe electrical steel sheets. Certain areas of the laminations that areconfigured to serve as flux barriers may be processed to suppressmagnetic permeability. To reduce the magnetic permeability of a certainarea, plastic deformation is introduced at these areas. The plasticdeformation may be introduced by deforming processes.

For example, a bridge region of a rotor lamination may be deformed toreduce magnetic permeability. The bridge region may be defined as thesurface area between the magnet openings that make up a V-shaped pair.As described earlier, the bridge region is that region of electricalsteel at the base of the V-shape at which point the magnet openingsassociated with a pair are at a closest distance. In addition, outerbridge regions may be defined as the surface of the lamination that liesbetween the distal ends of the magnet openings and the outer perimetersurface. There may be two outer bridge regions for each V-shaped pair ofmagnet openings.

To achieve a reduction in magnetic permeability, predefined regions maybe deformed by the methods to be described. The predefined regions maybe determined by analysis of the desired electrical device properties.For example, for a rotor lamination, the predefined regions may includethe bridge region and the outer bridge regions. The bridge region andthe outer bridge regions may be locally treated by various methods, suchas peening methods (e.g., including shot peening and laser peening). Amask may be created and placed over the lamination to expose only thebridge region and/or the outer bridge regions for deforming. Suchprocessing only changes the properties of the material in the exposedregion. Note that other predefined regions may be selected based on thedesired properties for a given electrical device. The predefined regionsmay be those surface areas of the lamination at which deformationresults in a decrease in magnetic permeability of the electrical core.

Another method of deforming the laminations may be to press thepredetermined regions to form one or more indentations or compressedregions in the predetermined regions (e.g., bridge region and outerbridge regions). Plastic deformation may be introduced by a punchingprocess. The punching process may apply a shearing force that createsplastic deformation at the cut edge. Additional plastic deformation canbe achieved during the punching process.

Electrical steel is commonly used in rotating electric machines, such asmotors, generators and the like. During operation, centrifugal force dueto rotation may stress rotor laminations. The stress of the laminationsmay affect the structural integrity of rotor core assembly via fatigue.

Referring now to FIGS. 12-19, an electric machine lamination may beformed using a combination of a punching process and additivemanufacturing process. A punching process may utilize punch toolingwhich may include a punch 400 (which may also be referred to as a punchhead). The punch tooling may also include a die 404. The punch toolingmay also include a blankholder and/or a dieholder.

In at least one approach, the punch 400 may include a leading portion,which may be referred to as a central region 410. The central region mayinclude a distal surface 412 and a peripheral surface 414 (which maycorrespond to a peripheral wall) that extends from the distal surface.The peripheral surface 414 may, for example, extend in a plane generallyorthogonal to the distal surface 412. In at least one approach, theperipheral surface 414 is a plurality of surfaces that together combinethe peripheral surface. In still another approach, the peripheralsurface 414 is a continuous peripheral surface.

The central region 410 of the punch 400 may have a cross-section thatmay correspond to an area to be punched in a sheet. For example, thecentral region 410 may be generally cylindrical such that the peripheralsurface 414 may define a generally circular cross-section. The centralregion 410 may be aligned with an aperture 420 or cavity formed in thedie 404. In this way, upon punching, at least a portion of the punchedmaterial may be expelled through the aperture 420.

The punch 400 may include a compression surface 416. The compressionsurface 416 may extend from the central region 410; for example, fromthe peripheral surface 414. In at least one approach, shown in FIG. 12,the punch 400 a may have a compression surface that may be a taperedpunch surface 416 a. The tapered punch surface 416 a may extend from theperipheral surface 414 at an oblique angle relative to the plan of theperipheral surface 414. The oblique angle may be, for example, in therange of approximately 30 degrees to approximately 60 degrees, and moreparticularly, in the range of approximately 35 degrees to approximately55 degrees, and may be, for example, approximately 45 degrees.

In still another approach, shown in FIG. 15, the punch 400 b may have acompression surface that may be a stepped punch surface 416 b. Thestepped punch surface 416 b may extend from the peripheral surface 414in a plane that may be generally orthogonal to the peripheral surface414.

In at least one approach, a method of forming an electric machinelamination may include disposing a sheet 430 on the die 404. Whendisposed on the die 404, at least a portion of the sheet 430 may extendover the aperture 420. The sheet 430 may have a first composition thatmay be, for example, an iron alloy.

The method may include punching the sheet 430. Punching the sheet 430may form an aperture or cavity in the sheet 430. In at least oneapproach, the punching includes punching through an entire thickness ofthe sheet 430 to form an aperture in the sheet. In still anotherapproach, the punching includes punching through less than the entirethickness of the sheet 430 to form a recess or cavity in the sheet 430.

The aperture may have a dimension (e.g., length or diameter) thatcorresponds to the geometry of the central region 410. In at least oneapproach, the punch (e.g., punch 400) may extend into the die 404 suchthat an interface of the peripheral surface 414 and the compressionsurface 416 engages the die 404. In still another approach, the punch(e.g., punch 402) may extend into the die 404 such that an interface ofthe peripheral surface 414 and the compression surface 416 does notengage the die 404. In this approach, less than an entire height of theperipheral surface 414 may extend into the aperture 410 of the die 404.

During a punching routine, the punch 400 may engage the sheet 430 andmay form a compressed region 434 of the sheet 430. In this way, punchingthe sheet 430 may form an aperture or cavity 432 in the sheet 430, and acompressed region 434 at a perimeter of the cavity 432. As such, thecompressed region 434 may have a geometry formed by (e.g., correspondingto) a geometry of the compression surface 416 of the punch 400. As shownin FIG. 13, the compressed region 434 may be a tapered compressed region434 a that extends about the cavity 432. As shown in FIG. 16, thecompressed region 434 may be a stepped compressed region 434 b thatextends about the cavity 432. In either approach, as shown in FIGS. 13and 16, a cross-section of the sheet 430 may a first thickness T1adjacent the compressed region 434, and a second thickness T2 at thecompressed region 434 that is greater than zero and less than the firstthickness T1.

FIGS. 12 and 15 depict the punch 400 and die 404 in a position duringthe punching operation. The central region 410 (or leading portion)penetrates the die 404 via the opening 412 defined by the die 404. Theoperation of the punch 400 and die 404 causes material to be removedfrom the sheet 430 (or lamination) and expelled via the die opening 410.As the central region 410 penetrates the die 404 via the die opening410, the compression surface 416 of the punch 400 further compresses theedges of the openings created in the sheet 430. The additionalcompression causes plastic deformation in the edges that define theopening in the sheet 430. The compression surface 416 of the punch 400may be configured to apply an equal amount of force to the entire edgeof the opening. The compression surface 416 of the punch 400 may also beconfigured to apply more force to predetermined edges. For example, aslope of the compression surface 416 may be varied around the punch 400for the openings. For example, the compression surface 416 may beconfigured to apply a greater amount of plastic deformation to thebridge region and/or the outer bridge regions.

Referring to FIGS. 13 and 16, the sheet 430 may be disposed on a bed440. A deposit material 450 may be deposited within the cavity 432 andon the compressed region 434. The deposit material 450 may have a secondcomposition that is different than the first composition of the sheet430. In at least one approach, the deposit material 450 is a powderedmetal. The deposit material 450 may be deposited from a single nozzle,or from a plurality of nozzles 452 disposed proximate a beam (e.g., alaser), as shown in FIG. 13.

In at least one approach, such as in DMLS and LD additive manufacturing,a beam 454 may be scanned along the deposit material 450. The beam 454may be an optical beam, such as a laser, that is emitted from an opticalsource 456. Scanning of the beam 454 along the deposit material 450 mayform a bound material 470 within the cavity 432 and on the compressedregion 434.

In still another approach, such as in cold spray additive manufacturing,the scanning with a beam may not be part of the forming process. In suchan approach, the cold spray of deposit material may result in boundmaterial 470 within the cavity 432 and on the compressed region 434.

In at least one approach, an electrically-insulating coating 472 may beapplied to the bound material 470. In still another approach, anelectrically-insulating coating 472 may be applied to the sheet 430 andto the bound material 470.

As such, in at least one approach, an electric machine lamination isprovided. The electric machine may include a sheet formed of an ironalloy and at least partially defining adjacent magnet pockets. The sheetmay include a tapered compressed region extending between and at anoblique angle to upper and lower surfaces of the sheet. The electricmachine lamination may further include a composition different than theiron alloy disposed at the tapered compressed region, extending betweenthe adjacent magnet pockets, and forming a center bridge having a lowermagnetic permeability than the sheet.

A cross-section of the sheet may have a first thickness adjacent thetapered compressed region, and a second thickness at the taperedcompressed region that is greater than zero and less than the firstthickness. An upper surface of the composition may be substantiallyflush with the upper surface of the sheet at the tapered compressedregion. A lower surface of the composition may be substantially flushwith the lower surface of the sheet. The tapered compressed region andthe composition at the tapered compressed region may define a combinedthickness that generally corresponds to a thickness of the sheetadjacent the tapered compressed region. The tapered compressed regionmay include a plurality of opposing tapered compressed regions. Thecomposition may be disposed at and may extend between the plurality ofopposing tapered compressed regions. The composition disposed betweenthe plurality of opposing tapered compressed regions may have athickness that generally corresponds to a thickness of the sheetadjacent the tapered compressed region.

In at least one approach, an electric machine lamination is provided.The electric machine lamination may include a sheet formed of an ironalloy and at least partially defining adjacent magnet pockets. The sheetmay include a reduced-thickness stepped region extending at leastpartially between the adjacent magnet pockets. The electric machinelamination may further include a composition different than the ironalloy disposed at the reduced-thickness stepped region, extendingbetween the adjacent magnet pockets, and forming a center bridge havinga lower magnetic permeability than the sheet.

The reduced-thickness stepped region may include a first interface(e.g., interface 480′ in FIG. 17) that extends in a plane substantiallyparallel to upper and lower surfaces of the sheet. The reduced-thicknessstepped region may include a second interface (e.g., interface 480″ inFIG. 17) that extends from the first interface in a plane substantiallyorthogonal to upper and lower surfaces of the sheet. In this way, asshown in FIG. 17, a cross-section of the electric machine lamination maydefine a T-shaped composition region embedded within the sheet. An uppersurface of the composition may be substantially flush with an uppersurface of the sheet at the reduced-thickness stepped region. A lowersurface of the composition may be substantially flush with a lowersurface of the sheet. The reduced-thickness stepped region and thecomposition at the reduced-thickness stepped region may define acombined thickness that generally corresponds to a thickness of thesheet adjacent the reduced-thickness stepped region. The composition maybe a non-ferromagnetic material. The sheet and composition may at leastpartially define a unitary multiple-composition rotor lamination.

In this way, a single electric machine lamination may be formed. Amethod may include forming a plurality of electric machine laminationutilizing one or more, or combination of, the steps previouslydescribed. In this way, a second electric machine lamination may beformed by punching a second sheet having the first composition to form acavity and a compressed region at a perimeter of the cavity. The secondelectric machine lamination may further be formed by depositing, withinthe cavity and on the compressed region, a deposit material having thesecond composition. The second electric machine lamination may furtherbe formed by scanning a beam along the deposit material to form a boundmaterial within the cavity and on the compressed region. The first andsecond electric machine lamination may be secured to each other to format least a portion of an electric machine. The process may be repeatedonce, twice, or three or more times to form an electric machinecomponent.

Referring to FIGS. 14 and 17, a unitary electric machine lamination 460may be provided. The unitary electric machine lamination may include asheet 430 that may be formed, for example, of an iron alloy. The sheet430 may include a core region 462, and a compressed region 434 that mayextend from the core region 462. The compressed region 434 may be formedby one or more punches, such as punches 400 a and/or 400 b. Thecompressed region 434 may have a thickness less than a thickness of thecore region 462.

The unitary electric machine lamination 460 may further have a depositedcomposition 470 that may be formed of a second material different thanthe that of the sheet 430. The deposited composition 470 may be disposedat one or both of the cavity 432 and the compressed region 434. In atleast one approach, the deposited composition 470 and compressed region434 may define a combined thickness that generally corresponds to thethickness of the core region 462.

As such, a unitary electric machine lamination 460 contemplated hereinmay have an integrated or embedded deposited composition (e.g., whenviewed along a cross-section of the lamination, or when viewed along atop plan view of the lamination). In this way, the unitary electricmachine lamination 460 may be referred to as a heterogeneous unitaryelectric machine lamination. The deposited composition may havedifferent physical properties than the lamination cores within atwo-dimensional plane. The differing physical properties may include oneor more of a) magnetic permeability, b) mechanical strength, c) loss,and d) magnetic flux density. As discussed, the deposited compositionmay be provided at one or more of the areas discussed elsewhere herein.

In at least one approach, the sheet 430 and the deposited composition470 may at least partially define a unitary multiple-composition rotorlamination. In still another approach, the sheet 430 and depositedcomposition 470 may at least partially define a unitarymultiple-composition stator lamination.

Although and punch-and-die assembly is discussed herein, it is expresslycontemplated that a mold may be configured to form one or moreindentations in an electrical steel sheet. A press machine may beconfigured with an upper mold and a lower mold. The upper mold may besecured to an upper press member. The lower mold may be secured to alower press member. The upper mold and the lower mold may be configuredto cooperate to form an indentation or a plurality of indentations in alamination that is placed in between. The upper press member and thelower press member may be configured to move relative to one another.The lamination may be positioned in the mold and the upper press memberand the lower press member. Pressure may be applied to the upper pressmember and/or the lower press member. The pressure forces the upper moldand the lower mold to move together resulting in an indentation beingformed in the lamination. The size, shape, and depth of the indentationsmay be configured to optimize the reduction of magnetic permeability foreach electric machine design. Other shaped indentations are possible.For example, the mold may have a wave-shaped cross section. Theindentations may be configured to have rounded edges, square/rectangularedges, or conical shape depending on the specific characteristicsdesired.

The pressing operation may be performed after the lamination is punched.Further, the pressing operation may be incorporated with the punchingoperation. The punch and die may be configured to punch the openings ofthe lamination and, during the same operation, form indentations in thepredetermined regions. The mold may be configured to form indentationsat the predetermined locations of the lamination. For example, apredetermined pattern of indentations may be formed in the bridge regionand/or the outer bridge regions. The pattern may be selected to tune themagnetic permeability of the region to a predetermined value.

In still another approach, a press machine may be configured with afirst mold secured to an upper press member and a second mold secured toa lower press member. Pressing the lamination may produce plasticdeformation through the whole of the predetermined regions. A laminationmay be inserted between the first mold and the second mold and pressed.The resulting lamination may form a curved cross-sectional profile inthose predetermined regions. The shape and curvature may be adjusted tomodify the magnetic permeability in the predetermined regions.

As discussed herein, a method of forming an electric machine laminationis provided. The method may include punching a ferromagnetic sheet. Thepunching of the ferromagnetic sheet may form a cavity at least partiallydefining adjacent magnet pockets. The punching of the ferromagneticsheet may further form a compressed region at a perimeter of the cavity.The method may further include constructing a center bridge. The centerbridge may have magnetic properties different than the ferromagneticsheet. The center bridge may extend from the compressed region betweenthe adjacent magnet pockets. The center bridge may be constructed bydepositing a non-ferromagnetic material within the cavity and on thecompressed region.

Referring now to FIGS. 18 and 19, a method of forming an electricmachine component 500 may include punching a plurality of sheets 502 toform a plurality of through-apertures 504. The sheets 502 may have afirst composition. The sheets 502 may be stacked to at least partiallyalign the through-apertures 504.

A deposit material 510 may be deposited within the through-apertures504. The deposit material 510 may have a second composition differentthan the first composition. As previously discussed with respect toFIGS. 13 and 16, in an optional approach, a beam may be scanned alongthe deposit material 510 to form a bound material within thethrough-apertures 504.

In at least one approach, the sheets 502 include an exterior sheet 502 ahaving an exterior through-aperture 502 a and an interior sheet 502 bhaving an interior through-aperture 502 b. The exterior sheet 502 a mayinclude a cross-sectional profile adjacent the exterior through-aperture502 a that is different than a cross-sectional profile adjacent theinterior through-aperture 502 b. As previously described, a punch may beutilized to punch the exterior sheet 502 a to form the exteriorthrough-aperture 504 a and a compressed region 506 at a perimeter of theexterior through-aperture 504 a. For example, with reference to FIG. 18,the compressed region 506 may be a tapered compressed region thatextends about the exterior through-aperture 504 a. With reference toFIG. 19, the compressed region 506 may be a stepped compressed regionthat extends about the exterior through-aperture 504 a. In at least oneapproach, the interior sheet 502 b may be substantially free of acompressed region at a perimeter of the interior through-aperture.

As such, an electric machine may be provided. The electric machine mayinclude a lamination stack that may include exterior laminations (e.g.,laminations 502 a) and interior laminations (e.g., laminations 502 b)disposed therebetween. The interior and exterior laminations may includeinner cutouts disposed in alignment. At least a portion of the innercutouts of the exterior laminations may have a width greater than innercutouts of the interior laminations. The electric machine may furtherinclude a core deposit having a lower magnetic permeability than thelamination stack disposed within the inner cutouts of the interior andexterior laminations. As shown in FIG. 18, the inner cutouts of theexterior laminations may have a stepped interface extending parallel toand planarly offset from exterior surfaces of the exterior laminations.As shown in FIG. 19, the inner cutouts of the exterior laminations mayhave a tapered interface extending between and at an oblique angle toexterior surfaces of the exterior laminations.

The exterior laminations may include a compressed region adjacent theinner cutouts of the exterior laminations. The interior laminations maybe substantially free of compressed regions adjacent the inner cutoutsof the interior laminations. Exterior surfaces of the core deposit maybe substantially flush with respective exterior surfaces of the exteriorlaminations.

In at least one approach, microscopic punching defects at the cuttingedge of electrical steel may be removed by a mechanical smoothingmethod. In one example, the electrical steel is first punched into thefinished shape, (e.g., a rotor lamination of an electric machine). Next,the laminations are stacked together to form a core, (e.g., a rotor coreof an electric machine). Lastly, the assembled core is then treated byforcibly propelling a stream of abrasive material (i.e., media) againsta pre-defined cutting surface of the rotor core to smooth the roughcutting surface of the microscopic defects. Aspects of the improvedfatigue life include smoothing cutting defects to prevent fatigue crackinitiation and inducing a compressive stress layer to prevent crackinitiation and propagation.

FIG. 20 depicts an example process flow for a method of increasingfatigue life in an electrical device. At operation 700, core laminationsare formed by punching a sheet of electrical steel resulting in one ormore cut edges. At operation 702, the laminations may be assembled intoa core such that an outer perimeter surface of the core is defined bythe cut edges. At operation 704, the predetermined surfaces may beblasted by the techniques that have been previously described. Forexample, the predetermined surfaces may include the top bridge surfacesof the rotor, namely an arc along the outer surface of the rotor and theinner surface within the openings formed in the core (e.g., magnetopenings). Also, the predetermined surfaces may include the centerbridge surfaces within the openings formed in the core (e.g., magnetopenings).

FIG. 21 depicts an example process flow for a method of increasingfatigue life in an electrical device. At operation 800, core laminationsare formed by punching a sheet of electrical steel resulting in one ormore cut edges. At operation 802, the laminations may be assembled intoa core such that an outer perimeter surface of the core is defined bythe cut edges. At operation 804, the assembled laminations are maskedexposing predetermined surfaces. For example, the predetermined surfacesmay include the top bridge surfaces of the rotor, namely an arc alongthe outer surface of the rotor and the inner surface within the openingsformed in the core (e.g., magnet openings). Also, the predeterminedsurfaces may include the center bridge surfaces within the openingsformed in the core (e.g., magnet openings). The masking may includeapplication of a polymer, masking tape, or other thin film or metalsheet to protect areas covered while leaving other areas exposed andsubject to the blasting. Alternatively, a nozzle may be able toselectively target specific areas (e.g., top bridge surfaces and centerbridge surfaces). Limiting the blasting to these areas may reduce thetime needed to process the laminations, thus reducing costs. Atoperation 806, the predetermined surfaces may be blasted by thetechniques that have been previously described. For example, thepredetermined surfaces may include the top bridge surfaces of the rotor,namely the arc along the outer surface of the rotor and the innersurface within the openings formed in the core (e.g., magnet openings).Also, the predetermined surfaces may include the center bridge surfaceswithin the openings formed in the core (e.g., magnet openings). Lastlyin operation 808, the masking material may be removed from the surfacevia mechanically removing the tape (e.g., peeling the tape off), or abath (plasma or wet bath) to remove the polymer. However, if the maskingwas done via mechanically directing the blast stream to the specificregions, then this operation would not be needed.

Although the description is applied to electric machines in a vehicleapplication, the methods described are applicable electrical devicesused in any field of application. The methods are applicable to otherrotating applications of electrical steel as well.

The methods of locally tuning physical properties of lamination coresthrough metal AM technologies is not limited to the DMLS and LDprocesses discussed herein. Other metal additive manufacturingtechnologies, such as direct metal laser melting, selective lasermelting, electron beam additive manufacturing and laser-engineered netshaping may also be utilized. It is contemplated that the proposedmethod to locally tune physical properties of lamination cores may useany suitable method that includes powder bed fusion and directed energydeposition related additive manufacturing technologies.

The proposed methods may also be utilized in cold spray additivemanufacturing, where fine powder is accelerated by a high-velocitycompressed gas jet. This powder then hits a substrate with sufficientkinetic energy to produce a dense layer of material. By changing thepowder composition, the local physical properties can be tuned duringthe lamination deposition process. As cold spray additive manufacturingis a relatively low temperature additive manufacturing process,additional flexibility in choosing insulation coating material usedbetween lamination layers may be available. To form a well bonded anddense deposit in the cold spray additive manufacturing process, thematerials may be plastically deformed upon impact, thereby creatingresidual stress and defects in the as-deposited material. Laminationcores made by cold spray additive manufacturing may be heat-treated torelease the residual stress and improve the physical properties.

Furthermore, the various approaches to locally tuning properties of anelectric machine component discussed herein may be combined, modifiedand combined, or otherwise used in conjunction with one another. Assuch, it is expressly contemplated that the various approaches to bothpunching and additive manufacturing described herein may be used inconjunction with one another.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms encompassed by the claims.The words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the disclosure. Aspreviously described, the features of various embodiments may becombined to form further embodiments of the invention that may not beexplicitly described or illustrated. While various embodiments couldhave been described as providing advantages or being preferred overother embodiments or prior art implementations with respect to one ormore desired characteristics, those of ordinary skill in the artrecognize that one or more features or characteristics may becompromised to achieve desired overall system attributes, which dependon the specific application and implementation. These attributes mayinclude, but are not limited to cost, strength, durability, life cyclecost, marketability, appearance, packaging, size, serviceability,weight, manufacturability, ease of assembly, etc. As such, embodimentsdescribed as less desirable than other embodiments or prior artimplementations with respect to one or more characteristics are notoutside the scope of the disclosure and may be desirable for particularapplications.

What is claimed is:
 1. A rotor comprising: a rotor core lamination thatincludes a first metal alloy that at least partially defines adjacentmagnet pockets proximate an outer periphery of the rotor corelamination, and a second metal alloy different than the first metalalloy that forms at least a portion of a bridge that extends between themagnet pockets; and permanent magnets disposed in the magnet pockets atopposing sides of the second metal alloy.
 2. The rotor of claim 1wherein the first metal alloy has a higher magnetic permeability thanthe second metal alloy.
 3. The rotor of claim 1 wherein the second metalalloy has a smaller grain size than the first metal alloy.
 4. The rotorof claim 1 wherein the second metal alloy defines peripheral bridgesthat extend between the magnet pockets and the outer periphery of therotor core lamination.
 5. The rotor of claim 1 wherein the second metalalloy extends about an entire outer circumference of the rotor corelamination.
 6. The rotor of claim 1 wherein the first metal alloydefines an air pocket disposed radially between an inboard region of therotor core lamination and the magnet pockets.
 7. An electric machinecomprising: a stack of interlocked rotor core laminations, individualrotor core laminations of the interlocked rotor core laminationsincluding a mortise extending therein and an integrally-formed tenonextending therefrom, wherein the tenons interface with the mortises tointerlock adjacent rotor core laminations.
 8. The rotor core of claim 7wherein a first individual rotor core lamination has a first mortisehaving a depth extending into the first individual rotor core laminationand a second individual rotor core lamination has a firstintegrally-formed tenon having a height extending therefrom, wherein theheight of the first integrally-formed tenon corresponds to the depth ofthe first mortise.